Shape from shading for non-Lambertian surfaces

It is known that most real surfaces are neither perfectly diffuse (Lambertian) nor ideally specular (mirror-like); however, most shape-from-shading algorithms assume Lambertian reflectance. It is necessary to develop new techniques to solve the shape-from-shading problem. These techniques must be able to recover the shape of objects whose surfaces are not necessarily Lambertian. A new heuristic-based algorithm, called the general shading logic algorithm, is proposed to recover the shape of objects whose surfaces are non-Lambertian. This algorithm is based on the shading logic algorithm recently proposed by Vega and Yang (see IEEE Transactions on Pattern Analysis and Machine Intelligence, vol.15, no.6, p.592-597, 1993). The proposed algorithm is flexible enough to work with a more general reflectance model. To demonstrate that the proposed algorithm can cope with a wide range of reflectance models, a physically-based model for light reflection is used that can approximate rough surfaces. The model of light reflection used is similar to the Torrance-Sparrow (1967) approach. The general shading logic algorithm has been implemented and evaluated experimentally. The experimental results of the proposed algorithm are very encouraging and the performance is demonstrated by extensive experiments using a wide variety of synthesized and real objects